The Longitudinal Labour Force Survey (LLFS) CURF is provided as a single flat file, which is hierarchically structured into 3 levels: Household/Dwelling, Family and Person. Furthermore, since the LLFS spans multiple time periods, the Survey month also acts like an additional level in the hierarchy. There are 5 identifiers that relate to these levels:

Every Survey Month has a 4 digit character, [ABSMID], which represents the year and month.

Each Household/Dwelling has a unique thirteen character identifier, [ABSHID]. This identifier is consistent across all months of selection in the Labour Force Survey (LFS).

On the Family level, each family within the household is numbered sequentially, [ABSFID], in each individual Survey month. This is to account for changes in family structure in households across the months of selection. The combination of month, household and family identifier uniquely identifies the family.

A Person identifier, [ABSPID], is assigned to each person sequentially within a household across all months of selection. On the person level, the combination of household and person identifier uniquely identifies the person. Alternatively, the Record ID [ABSRID], a unique 15 character identifier, can be used to uniquely identify a person across all months of the CURF. Most data items in the LLFS CURF relate to the person level.

People in special dwellings (see Residence Status [URSTATC]) are treated as lone individuals with no family characteristics. Each person in a special dwelling is assigned their own unique Household ID [ABSHID]. The ID is assigned to the person rather than the dwelling. This is because;

Any relationships that exist between people in a special dwelling are not recorded in the LFS, so no additional information can be gained from grouping people who were interviewed in the same special dwelling.

Special dwellings are assembled as cross-sectional ('point-in-time') measurements and are not linked longitudinally. This is because there can be no certainty in making links to records across time, as the people interviewed in hotels, prisons, boarding schools, etc. are subject to change.

[ABSHID] is sufficient to identify a person in a special dwelling, but [ABSRID] may also be used for consistency.

In summary, to specify particular levels, the following identifiers must be used:

Since the LLFS CURF is provided as a single flat file, there is no need to copy identifiers across different datasets - everything is provided in the one file. The identifiers are provided to allow analysis across the levels, although most analysis will relate to the person level, to which most of the data items relate. The Household and Family levels are mainly provided to outline family and household relationships between the people selected in private dwellings.